Presidencies begin with a slate wiped clean and a first 100 days in which the new incumbent sets out to change the world.

They end in the tawdry process in which George W Bush is now engaged: a final flurry of presidential decrees to prolong power beyond the grave, a concerted effort to regild a tarnished reputation — and, of course, pardons.

For months now, Bush has been issuing new regulations and notices to tie the hands of the Obama administration. The practice is not new: one of the worst previous offenders was none other than the deeply virtuous Jimmy Carter. But this Bush has indulged it far more than either his father or Bill Clinton. At the last count he has signed more than 100 such |orders — in effect, new laws that don't need to be approved by Congress — and more are likely during his last fortnight in office. And if you're a liberal or an environmentalist, or just a run-of-the-mill Democrat, you'll hate them.

Among other things, these ‘midnight rules’ clear the way for developing oil shale deposits on government land and make it easier for coal companies to dump strip-mining waste into local rivers. It will now be easier to build a coal-fired power station near a national park. In these same national parks, moreover, you may henceforth carry a loaded or concealed gun. A separate regulation chips away further at abortion rights, while another allows truckers to drive for longer periods without compulsory rest. Other changes weaken the Endangered Species Act and loosen federal rules on factory farming.

Last-minute regulations will be easy to unpick, but others less so. Some executive orders, with an impact of at least $100m a year, were published at least seven weeks ago, so they will have completed the required 60-day waiting period to become law by the time Barack Obama takes over.

‘Midnight rules’ are one way to try to reshape a presidency. Another is the media blitz that Bush and his acolytes have been conducting. For most of his term, Bush was sparing with interviews, but in the past few weeks he's given a dozen or more, talking up his achievements (yes, there have been a few, such as increased |assistance to Africa, especially to fight Aids, and the ‘No Child Left Behind’ education bill) and |skating over the rather more |numerous failures.

Bush, of course, famously hates putting himself on the couch, claiming that he's been too busy making history to worry about what the scribblers think about him. But sooner or later, every president gets the legacy bug. His valedictory interviews have been true to form: a few regrets, above all over those non-existent WMD in Iraq, but not the hint of an apology. Those who want to read more about his ‘freedom legacy’ across the Middle East, and the glories of extended prescription drug benefits for the elderly, can take comfort from the book Bush is planning to write.

In the meantime, his senior aides are already rewriting history. You thought Dick Cheney secretly ran US foreign policy, at least in Bush's first term? “Hooey,” Stephen Hadley, the meek and mild National Security Adviser, told The Washington Post last week. You thought the 43rd President was an incurious and arrogant ideologue who would not listen to anyone who disagreed with him? Wrong again. “The President is very good about hearing and wanting contrary advice,” chimed in Josh Bolten, the White House chief of staff. Everyone who deals with Bush “appreciates what a good leader he is, how smart he is and especially, how humane he is”. And, Bolten might have added, maybe what a voracious reader he is.

That unexpected insight emerges from a remarkable Boxing Day column in The Wall Street Journal by Karl Rove (remember him?) in which the man once described as ‘Bush's Brain’ claims the President devours books, getting through no fewer than 95 in 2006 alone, including L'Etranger by Albert Camus (presumably in translation, but who knows?)| Anyway, so much for the ignorant Texan hick we spent the past eight years mocking. Bush, it turns out, is a bona fide intellectual. Thus are images reburnished, even transformed. Might Rove be, shall we say, massaging the truth? Perish the thought.

Finally, there are the pardons. In fact, Bush has been surprisingly stingy in exercising this presidential prerogative. Of 8,000 applications for pardons, he had granted just 191 as of Christmas, fewer than either Ronald Reagan or Bill Clinton, who infamously pardoned the indicted financier (and generous Democratic party donor) Marc Rich in the final hours of his presidency. Bush has also commuted eight other sentences, most notably the jail term handed in 2007 to Lewis Libby, Cheney's one-time chief of staff, for perjury. There were expectations Libby might be granted a full pardon, but, thus far at least, not so. Among those who have requested pardons are Michael Milken, Wall Street's former junk bond king, the bribe-taking former Congressman Randy ‘Duke’ Cunningham, the disgraced Olympic champion Marion Jones, and of course our old friend Lord Black of Crossharbour.

But there is one problem for the departing Bush that neither a special ‘midnight rule’ nor any amount of history rewriting, and perhaps not even a pardon, will make disappear. I refer to the alleged war crimes committed by his administration: its refusal to comply with the Geneva Conventions, its forced ‘rendition’ of terrorist suspects to countries where it knew they were likely to be tortured, and above all its own use of torture.

Already Cheney and the former defence secretary Donald Rumsfeld, among others, will be carefully checking future foreign travel plans, to avoid a ‘Pinochet situation’ — when the former Chilean dictator was arrested in Britain in 1998 on a warrant issued by a Spanish magistrate for atrocities committed against Spanish |citizens.

But a separate threat also exists, of possible legal action within the US itself, prompting speculation that Bush could issue pre-emptive pardons to top officials at the White House, the Justice Department and the Pentagon who were responsible for drawing up the ‘coercive’ interrogation rules, and to the CIA personnel who put them into practice.

Such a step would not be new. Gerald Ford pardoned Richard Nixon just a month after taking |office in 1974, while Bush's own father pardoned Reagan's former defence secretary Caspar Weinberger on Christmas Eve 1992, to spare Weinberger trial on felony charges arising from the Iran-Contra scandal. But it would be political dynamite. As he tries to push through an emergency economic recovery package, the last thing Obama wants is a distracting and bitter row with the Republicans, stoking up the partisanship he has pledged to reduce.

But sooner or later something will happen. The stain on the country's reputation is too large, the outrage at the violation of the US constitution too great, and America's sense of decency and justice (albeit sometimes delayed justice) too ingrained for the whole torture scandal to be swept under the rug for ever.

“We owe the American people a reckoning,” Eric Holder, the incoming Attorney General, is on record as saying, and sooner or later that reckoning will come. Maybe a special prosecutor will be appointed, or perhaps Congress will carry out an investigation along the lines of the 1975 Church Committee that probed the misdeeds of the CIA. One way or another, Bush will have plenty to think about when he's not writing his memoirs (and reading books) in the golden years ahead.